Cen54261ch07qxd 111803 957 am page 332 332

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Unformatted text preview: tion of entropy generation Q Tsurr (b) The wall is considered Q Tsys Q Q Tsurr (c) The wall as well as (c) the variations of temperature (c) in the system and the (c) surroundings are considered FIGURE 7–70 Graphical representation of entropy generation during a heat transfer process through a finite temperature difference. cen54261_ch07.qxd 11/18/03 9:57 AM Page 332 332 FUNDAMENTALS OF THERMAL-FLUID SCIENCES SUMMARY The second law of thermodynamics leads to the definition of a new property called entropy, which is a quantitative measure of microscopic disorder for a system. The definition of entropy is based on the Clausius inequality, given by Q T 0 1. Pure substances: s s2 Any process: Isentropic process: s1 s2 s1 (kJ/kg · K) (kJ/K) 2. Incompressible substances: where the equality holds for internally or totally reversible processes and the inequality for irreversible processes. Any quantity whose cyclic integral is zero is a property, and entropy is defined as dQ T dS s1 T2 Isentropic process: Cav ln T2 T1 T1 (kJ/kg · K) (kJ/K) int rev For the special case of an internally reversible, isothermal process, it gives S s2 Any process: Q T0 3. Ideal gases: a. Constant specific heats (approximate treatment): Any process: s2 s1 Cυ, av ln T2 T1 R ln υ2 υ1 (kJ/kg · K) s2 s1 Cp, av ln T2 T1 R ln...
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This document was uploaded on 11/28/2012.

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